Method of forming corrugations



Aug, 23, 13% c. DE GANAHL 291259427 METHOD OF FORMING CORRUGATIONS E iled March 25, 19:57 2 Sheets-Sheet 1 IINVENTCJFH Aug. 2, 1938.

C. DE GANAHL METHOD OF FORMING CORRUGATIONS Filed March 25, 1937 v 2 Sheets-Sheet 2 INVENTOR 65m D'ZW/Vf/L,

wTbsw Patented Aug. 2, 1938 2,125,427

UNITED STATES PATENT OFFICE 2,125,427 METHOD OF FORMING CORRUGATIONS Carl de. Ganahl, Bristol, Pa., assignor to Fleetwings, Inc., Bristol, Pa., a corporation of Delaware Application March 25, 1937, Serial No. 132,916

7 Claims. (01. 153-76) This invention relates to a method of forming Fig. 1 represents a fragmentary plan of a uniform corrugationsin hard resilient sheet metal sheet of metal with cooperating aligning notches and the product that results therefrom. formed in the selvage margin, or side edges,

Sheet metal, such for instance as stainless Fig. 2 represents a fragmentary diagrammatic 5 steel, as used in aircraft and the like, is a hard edge elevation of a conventionally corrugated resilient sheet requiring appreciable force for sheet of metal, showing the straight or planar suitable working, and tending to resilient springside walls which are avoided by the invention ing, or partial shape recovery, after distortion herein, incident to a dieing or stamping operation. Fig. 3 represents a fragmentary diagrammatic it) Stainless steel corrugated sheets for aircraft reedge elevation of a continuously curved nonquire extreme accuracy in formation, in order sinusoidal corrugated sheet according to this that overlapping sheets may substantially exinvention, actly register, without undue strain or stress. Fig. 4 represents a fragmentary enlarged sec- For many reasons such corrugated sheets are tion of the metal sheet and the cooperating die 1'5 more desirable when the corrugations are not of members for securing the initial bend in the true sinusoidal form but instead are formed of sheet, to establish the continuously curved side continuously curved mutually tangential inter- Walls as an initial step, as shown by the full secting arcuate corrugations. Owing to the lines from which the sheet springs to the positoughnes's, hardness, and resilience of the steel tion shown in dotted lines after the die is opened,

Cir

. sheets, it is found that forming the corrugations Fig. 5 represents a perspective of the separated according to past practices is unsatisfactory and die members of the final apex-forming bending results in a generally sinusoidalcorrugated sheet step,

which is lacking in uniformity and strength. Fig. 6 represents diagrammatically the devel- Specifically, a defect of the past constructions, opment in completed stages of the completed among others, in which the corrugations were corrugation according to the invention, 25

formed from the flat sheet by pressure upon Fig. 7 represents diagrammatically the develwhat ultimately become apices of the corrugaopment in intermediate and final stages of the tions-was that this formed partially cylindrical positioning of the side wall of the corrugation or arcuate curves extending in opposite direcrelative to the initial fiat sheet.

tions of the sheet, connected, not by intersecting Referring to Fig. 2, there is shown a corrugated ,30 arcs of continuous curvature, but by substantially sheet l0 comprising partially cylindrical apices straight or flat side Walls merging substantially H to adjacent ones of which the fiat side walls tangentially into the partially cylindrical apices. l2 are respectively substantially tangential. It This is because with the dieing pressure subwill be understood that as usually formed pres- 5 stantially normal to the flat sheet and substansure is applied on and normal to the part of the tially incapable of exerting any lateral pressure, sheet which is to become the apex, and the fiat no direct pressure is exerted to shape the side sheet between those points is simply turned about walls of the corrugations, which therefore reand pulled or stretched between the adjacent tain the substantially fiat formation of the apices. It will be obvious that this sinusoidal original sheet. sheet is lacking in certain characteristics as com- 40 a It is among the objects of this invention: to pared to the continuously curved corrugated provide a method of corrugating sheet metal; sheet shown in Fig. 3. In this figure the corruto provide a method for forming sheet metal gations are continuously curved and are interwith uniform corrugations; to provide a method sectingly mutually tangential to each other.

5 for forming truly arcuate non-sinusoidal corru- In Fig. 3 the side walls I 2 are considered to gation's in a sheet of metal; to provide steps in extend between the parallel vertical lines intera corrugating method by which the side walls secting the curved sheet, and, as noted, are conof the corrugations are formed before the apices tinuously curved. The parallel vertical lines inthemselves; to provide a method for corrugating tersecting the corrugated sheet of Fig. 2 delinesheets to insure exact parallelism between adjaate the side walls l2, which are substantially oent corrugations; and many other objects and planar. advantages as will become more apparent as the Referring to Fig. '7, there is disclosed a diagram description proceeds. in which the flat sheet shown at A is given an In the accompanying drawings forming part initial dieing or stamping operation, as in the of this specification: dies shown in Fig. 4, to impart an initial curva- 55 ture to the sheet, as shown at A1 from which, when released, the sheet springs back to substantially the curvature shown at B, marking the completion of the initial bending step and the completion of the side wall 22 of the corrugation. The sheet is then subjected to the final bending operation as in the dies shown in Fig. 5, which engages and bends the flat material between the side walls (22) and a portion of the extremity of the bent side wall, as there is usually an overlap of the material worked in the primary and final bending strips, causing the material in the bent position B to be distorted or swung substantially to the bent position indicated at B. After release from the dies the bent sheet springs open again to assume the position C, the final completed form in which the curved side wall merges into the curved apex or crest of a corrugation asa continuous arc. While diagram Fig. 7 shows the successive positions and attitudes during the three positions of unstressed and two positions of die distorted stressed and compressed material, it is particularly shown to illustrate the side wall development.

In Fig. 6 the diagram shows the successive final positions of the crest or apex of a corrugation developed from the flat sheet, showing the movement of the side wall as it is both turned and moved laterally into proper tangential relation to the arcuate apex of the corrugation.

It is a factor of importance in this invention that the corrugations are mutually parallel. To insure this the sheet A is provided in the margins with carefully measured and located notches arranged in laterally aligned pairs-as l! 5, iii-4t, l'l-ll, !8l8, 2020, 2l2l, etc. Although illustratively shown as spaced across the lateral width of the sheet metal strip,it is also contemplated that they will be longitudinally spaced and aligned. Each pair is to locate and rigidly maintain the crest, apex, or line of symmetry of a corrugation. Notches I6-l6 (for instance) will be aligned with the apex of a corrugation presenting open side in one direction, as vertically upwaii'd (Fig. 6) while notches I '|--I'l will be aligned with the apex of the next adjacent corrugation presenting its open side in the other direction (vertically downward Fig. 6) and with area 22 (Figs. 1 and 6) forming the continuously curved wall between the curved crests of the corrugations.

Referring to Fig. 4, a pair of dies is shown, comprising a bottom male die 23, having a vertical stud 24 received in a recess 25 of the complemental female die 26. It will be understood that the dies 23 and 2'6 are of suficient length as to receive the entire length of metal between notches, and that pin or stud 24 and recess 25, have counterparts toward the other end of the die (not shown). The pins engage in the notches of a pair to loclc the sheet against movement during dieing operations. Preferably there will be several recesses arranged to mount pins 24, and several cooperating recesses in the dies, so arranged as to be adjustable for various widths or lengths of material to be corrugated.

Die 23 is provided with elongated plateaulike center section 2'! symmetrical relative to the pinv 24, curving downwardly on each side by the intersecting mutually tangential curved surfaces 28 and 30, merging into substantially horizontal longitudinally extending lateral margins 3| The female die 26 has a lower surface 32 the comple-' ment of that of the male just described, making due allowance (in both dies) for the gauge of metal to be treated.

It is a factor of moment that the radii of arcu ate surfaces 28 and 30, and of their complements in female die 26 be calculated and predetermined in accordance with the resilience of the various gauges of sheet metal contemplated to be used, in order to utilize the attendant spring back to open the die-impressed curves to the desired finished contour. This change in radius is substantially a linear function of the change in gauge of the metal to be treated.

Afterthe sheet has been disposed on the male die 2 with notches [6 (for instance) on the pins 24, the female die 26 is forced down upon the sheet (in Fig. 4) causing it to assume the form shown in that figure. This subjects the material 22, between laterally spaced notches, to be bent in the reentrant curve shown as a result of vertical pressure on the sheet. Note in Fig. 4 that the portionof the sheet adjacent to notch l6 between the curved portions remains substantially flat. It is this flat portion that in the next step becomes "the apex or crest of the corrugation. The initial or preliminary die stamping operation does nothing to the fiat portion, the ultimate curved apex, but simplyworks and contours area 22, as indicated in Fig. 6. Preferably all of the areas 22 between notches are given the preliminary diepressing before the final step is taken.

In the final processing step the sheet, preferably after completion of all of the initial steps, is positioned on the male die 33. This die has centering studs or locating studs 34, similar to those described in connection with Fig. 4,. and is preferably a substantially cylindrical or partially cylindrical member of narrower formation, or of smaller lateral diameter than the internal diameter of the finished apex of the corrugation. This again is predetermined in accordance with the gauge of metal being treated.

Notches l6 are again disposed in embracing relation to the ears or studs 34 so as to center the ultimate crest or apex on the crest of the die. The female semi-cylindrical die engages the upper surface of the relatively fiat portions between areas 22, and compresses it about die 33. The contact between the male and female die ,may comprise an area stopping at, or (and preferably) slightly overlapping the edges of the previously working areas 22, as indicated in clotted lines 36 in Fig. 3. It will be understood that suitable recesses 37 will be provided in the female die to receive pins 34, and the adjnstability as to length by repositioning pins 3d will also be obvious.

In Fig. 5, it is assumed that all of the upper curved surfaces containing the crests or apices have been given the final treatment as shown,

and the dies have been separated after forming the last complete corrugation, along line iii-l6. lhe fact that the sheet is turned over for alternate corrugations in the final step, and that the compressed position of the final step is preliminary to its release and resilient slight expansion to' form the desired substantially continuously curved corrugations desired of the sheet will be understood. It will also be understood that there are no retained stresses of any moment in the sheets, no metal is caused to fiow for the result, and the accuracy of the corrugations and strength, visual attractiveness and utility of the sheet will be obvious.

I claim:

1. The method of forming parallel corruga- III tions in a sheet of metal which comprises forming registering pairs of guide means on opposite sides of a sheet with each pair in predetermined laterally spaced relation to adjacent pairs, in using a pair of guide means to hold the sheet against movement while forming side walls of corrugations of the metal between the lines extending'between pairs of guide means, then of using a pair of guide means to hold the sheet against movement while forming a corrugation apex between the pro-formed side wall areas.

2. The method of corrugating a hard resilient sheet of metal which comprises the steps of dieing the metal between dies of more acute curvature than is ultimately desired to form curved side wall portions, releasing the metal from the die to permit its expansion to the desired side wall contour, then dieing the metal between the prepared contoured side Walls on a curvature more acute than the desired apex contour to form an apex of a corrugation between contoured side walls, then releasing the sheet from the latter die and permitting its expansion substantially to the desired contour of the corrugation.

3. The method of forming corrugated sheets with side walls between corrugations comprising continuously curved mutually tangential surfaces, which comprises dieing out a flat sheet with dies acting normally of the sheet, to form a sheet having the continuously curved mutually tangential surfaces disposed between flat surfaces, and then in dieing the flat portions between the curved surfaces by dies normal of the sheet to shape the flat portions into curved apices merging into the preformed curved side.

4. The method of forming corrugated sheets with continuously curved side walls between curved corrugation apices which consists first in holding the flat sheet and in dieing out a pair of spaced continuously curved side walls formed by two oppositely extending mutually tangential intersecting substantially arcuate portions adjacent a flat portion, and then in holding the sheet and dieing the flat portion to form the curved apex of a corrugation symmetrically between adjacent side walls as a curved continuation of the adjacent arcuate portions only thereof.

5. The method of forming corrugations in a relatively flat sheet of metal which comprises the steps of first forming a complemental pair of spaced curved side walls formed by two oppositely extending mutually tangential intersecting substantially arcuate portions in the flat sheet adjacent to and separated by relatively flat portions of the sheet, and then forming the curved apex of the corrugation from the relatively flat portion between the formed side walls as a substantial continuation of the respective adjacent arcuate portions only of said side walls.

6. The method of forming corrugations in a relatively flat sheet of metal which comprises the steps of first forming simultaneously a complemental pair of spaced curved side walls formed by two oppositely extending mutually tangential intersecting substantially arcuate portions in the flat sheet on opposite sides of a flat portion substantially parallel to the general plane of the sheet, and then forming the curved apex of the corrugation from the relatively flat portion between and as a merging continuation of the adjacent arcuate portions only of the formed side walls.

7. The method of forming corrugations in a relatively flat sheet of metal which comprises the steps of first forming a curved side wall formed by two oppositely extending mutually tangential intersecting substantially arcuate portions between relatively flat portions of the sheet, and then in forming the flat portions on each side of the curved wall into curved apices of corrugations merging into the respective adjacent arcuate portions of curved side Wall as continuations thereof.

CARL DE GANAHL. 

